Leads having electrodes implanted in or about the heart have been used to reverse life-threatening arrhythmia or to stimulate contraction of the heart. Electrical energy is applied to the heart via an electrode to return the heart to normal rhythm. Leads are usually positioned on or in the ventricle or the atrium and the lead terminals are attached to a pacemaker or defibrillator which is implanted subcutaneously.
One issue concerning, for example, pacemaker leads is the increase in stimulation threshold, both acute and chronic, caused by the interaction between the electrode and body tissue at the point of implant. Approaches to reducing the threshold include the incorporation of drug-eluting collars or plugs containing dexamethasone into the lead body. However, the size constraints imposed on the plug or collar matrix by the lead design limit the pharmacological therapy that can be provided to treat the complex nature of the natural healing process. Moreover, these devices many not adequately address many of the physiological processes involved in the healing response upon lead implantation.